A modified version of "The Other Two" (/g/28520/a822db6417/). Not sure which came first.
The other two would be Shiho and Masashi, as oposed to Akari and Hiroyuki, who would be the main two.
I've been using トゥハート for the name in Japanese Script, as it's the standard in e-hentai, but usually it appears in Japanese sites as To Heart. See the suruga-ya link for instance.